Explanation: Some functions are implemented both in libc and libc++.
Clang uses the enable_if attribute to resolve otherwise ambiguous
functions calls. This PR makes the name lookup aware of this attribute.
Issue: rdar://152192945
Risk: Low, only C/C++ APIs with enable_if attributes are affected.
Testing: Regression test added.
Original PR: #82019
Reviewer: @hnrklssn